Structural dependence of PFAS oxidation in a boron doped diamond-electrochemical system
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2024-01-03 |
| Journal | Environmental Research |
| Authors | Fatemeh Asadi Zeidabadi, Ehsan Banayan Esfahani, Raphaell Moreira, Sean T. McBeath, E. Johan Foster |
| Institutions | University of Massachusetts Amherst, University of British Columbia |
| Citations | 21 |
Abstract
Section titled āAbstractāDriven by long-term persistence and adverse health impacts of legacy perfluorooctanoic acid (PFOA), production has shifted towards shorter chain analogs (C4, perfluorobutanoic acid (PFBA)) or fluorinated alternatives such as hexafluoropropylene oxide dimer acid (HFPO-DA, known as GenX) and 6:2 fluorotelomer carboxylic acid (6:2 FTCA). Yet, a thorough understanding of treatment processes for these alternatives is limited. Herein, we conducted a comprehensive study using an electrochemical approach with a boron doped diamond anode in Na<sub>2</sub>SO<sub>4</sub> electrolyte for the remediation of PFOA common alternatives, i.e., PFBA, GenX, and 6:2 FTCA. The degradability, fluorine recovery, transformation pathway, and contributions from electro-synthesized radicals were investigated. The results indicated the significance of chain length and structure, with shorter chains being harder to break down (PFBA (65.6 Ā± 5.0%) < GenX (84.9 Ā± 3.3%) < PFOA (97.9 Ā± 0.1%) < 6:2 FTCA (99.4 Ā± 0.0%) within 120 min of electrolysis). The same by-products were observed during the oxidation of both low and high concentrations of parent PFAS (2 and 20 mg L<sup>-1</sup>), indicating that the fundamental mechanism of PFAS degradation remained consistent. Nevertheless, the ratio of these by-products to the parent PFAS concentration varied which primarily arises from the more rapid PFAS decomposition at lower dosages. For all experiments, the main mechanism of PFAS oxidation was initiated by direct electron transfer at the anode surface. Sulfate radical (SO<sub>4</sub><sup>ā¢-</sup>) also contributed to the oxidation of all PFAS, while hydroxyl radical (<sup>ā¢</sup>OH) only played a role in the decomposition of 6:2 FTCA. Total fluorine recovery of PFBA, GenX, and 6:2 FTCA were 96.5%, 94.0%, and 76.4% within 240 min. The more complex transformation pathway of 6:2 FTCA could explain its lower fluorine recovery. Detailed decomposition pathways for each PFAS were also proposed through identifying the generated intermediates and fluorine recovery. The proposed pathways were also assessed using <sup>19</sup>F Nuclear Magnetic Resonance (NMR) spectroscopy.
Tech Support
Section titled āTech SupportāOriginal Source
Section titled āOriginal SourceāReferences
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